The present invention relates to a color cathode ray tube and, more particularly, to a color cathode ray tube of a multineck structure.
Color cathode ray tubes have received a great deal of attention as high-quality broadcast image display devices or computer terminal high-resolution graphic display devices. For these applications, increased resolution has been an issue. High resolution in a color cathode ray tube can be achieved by minimizing an electron beam spot on its phosphor screen. However, in order to minimize the electron beam spot, the electrode structure of the electron gun assembly must be improved, or the electron gun assembly itself must be elongated and enlarged to increase its diameter. However, a large electron gun assembly cannot provide a sufficiently small electron beam spot due to the following reason. The larger the size of the color cathode ray tube, the longer the distance between the electron gun assembly and the phosphor screen, giving the electron lens an undesirably large magnification. In order to achieve high resolution in a large cathode ray tube, it is important to decrease the distance between the electron gun assembly and the phosphor screen. For this purpose, the tube can be constituted by a wide-angle deflection tube. However, in such a tube, the magnification at the central portion of the screen differs from that at the peripheral portion thereof.
In order to solve the above problem, Japanese Patent Disclosure (Kokai) No. 48-90428 describes a multi-tube structure display device having a plurality of small or medium cathode ray tubes arranged in the horizontal or vertical direction to display an image on a large screen with high resolution.
A conventional display device of the multi-tube structure can be effectively used outdoors to display an image on a very large screen divided into blocks. However, the display device is not suitable for a medium screen size, i.e., about 40", since the joints of the divided blocks of the screen stand out and result in a poor image. In particular, when this display device is used as a computer-aided design graphic terminal, the presence of joints becomes a decisive shortcoming.